Aklakan commented on issue #3837:
URL: https://github.com/apache/jena/issues/3837#issuecomment-4205537791
> The outer requests are being canceled by the client, but the inner SERVICE
subqueries
continue to run. After enough of these, the target dataset stops responding
to even direct
queries.
If I understand the problem correctly, then the issue is, that cancellation
is not forwarded to a SERVICE execution, and the requests just keep piling up.
Service execution materializes the result sets before returning -
cancellation only kicks in after materialization completes. Especially when
doing `?s ?p ?o`, executions will likely pile up.
However, setting `arq:httpQueryTimeout` in the Fuseki endpoint context
*should* have an effect for HTTP SERVICE requests (based on the code).
*Might* work also work with the CLI tooling: (not tested)
```
# Whichever tool you are using
./rsparql --set 'arq:httpQueryTimeout=1000' ...
./tdb2-query --set `arq:httpQueryTimeout=1000` --set 'arq:queryTimeout=2000'
# Note: queryTimeout should affect the outer query, httpQueryTimeout the
inner.
```
Relevant code in `Service.java`
```java
public static QueryIterator exec(OpService op, Context context) {
/...
long timeoutMillis = timeoutFromContext(context);
// RegistryServiceModifier is applied by QueryExecHTTP
Params serviceParams = getServiceParamsFromContext(serviceURL,
context);
// Build the execution
try (QueryExecHTTP qExec = QueryExecHTTP.newBuilder()
.endpoint(serviceURL)
.timeout(timeoutMillis, TimeUnit.MILLISECONDS)
.httpHeader(HttpNames.hUserAgent, HttpEnv.UserAgent)
.query(query)
.params(serviceParams)
.context(context)
.httpClient(httpClient)
.sendMode(querySendMode)
.build()) {
// Detach from the network stream.
RowSet rowSet = qExec.select().materialize();
QueryIterator qIter = QueryIterPlainWrapper.create(rowSet);
if (requiresRemapping)
qIter = QueryIter.map(qIter, varMapping);
return qIter;
} catch (HttpException ex) {
throw QueryExceptionHTTP.rewrap(ex);
}
// ...
}
// ---------------
/*package*/ static long timeoutFromContext(Context context) {
return parseTimeout(context.get(httpQueryTimeout));
}
```
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